With older Americans being more at risk for glaucoma and that same population taking multiple prescription medications, it’s important for primary care physicians to understand the side effects and possible drug interactions of the various prescription glaucoma eye drops, says Anita Campbell, MD, a fellowship-trained glaucoma specialist with Grene Vision Group in Wichita.
According to the American Academy of Ophthalmology, people over age 60 are at an increased risk for glaucoma. People in that age demographic also take multiple prescriptions, according to a 2019 poll by the Kaiser Family Foundation, a nonprofit that tracks health issues. Nearly 90% of Americans ages 65 and older and nearly 75% of 50- to 64-year-olds take prescription drugs, the study found.
For this article, Dr. Campbell talks about four major classes of antihypertensive eye drops used to treat glaucoma and their potential side effects and interactions, which can be helpful for physicians in determining causes of certain symptoms or in prescribing drugs that can interact with glaucoma medication. As newer glaucoma drugs are being developed, new drug classes are being added to the glaucoma treatment arsenal, but they have fewer systemic side effects, Dr. Campbell said. Many glaucoma patients require treatment with eye drops in different classes.
Systemic side effects are more likely to occur if the patient doesn’t follow directions to facilitate the drop being absorbed in the eye. One minute of eyelid closure allows >90% ocular absorption. The remaining medication drains through the nasolacrimal duct into the vascular nasopharyngeal mucosa where systemic absorption can occur. Some sources recommend digital pressure near the bridge of the nose to prevent flow through the nasolacrimal duct, but it is hard for patients to find this landmark, so Dr. Campbell does not recommend it.
Alpha-2 Adrenergic Agonist
A commonly prescribed eye drop in this class is brimonidine, which decreases the production of intraocular fluid to reduce pressure. This drug may cause dizziness or dysequilibrium. Dr. Campbell avoids this medication in patients at risk of falls, such as the elderly or those using canes or walkers. The drug may also cause other symptoms such as lethargy, headaches and dryness in the mouth and nose.
Timolol, one of the earliest eye drops prescribed to treat glaucoma, falls into this class. Drugs in this class also decrease the production of intraocular fluid, but also have the systemic risks of other beta blockers such as hypotension and bradycardia. It may affect a person’s exercise tolerance, “like hitting that wall quicker during a workout,” Dr. Campbell says. For patients with asthma or COPD, it can cause shortness of breath via bronchoconstriction. It may also increase depression symptoms. If it is necessary to prescribe a beta blocker for a patient with these underlying conditions, a cardioselective one such as carteolol is preferred.
Carbonic Anhydrase Inhibitors
This medication, which decreases production of intraocular fluid, is available in either eye drop form or pill form. Although drugs in this class contain nonantibiotic sulfonamides, only 10% of patients with a sulfa (antibiotic sulfonamide) allergy will have topical reactions because of the difference in metabolite form. However, those same patients cannot take acetazolamide in pill form, Dr. Campbell says. Other side effects with the pill form include kidney stones, upset stomach and frequent urination.
Drugs in this class increase intraocular fluid outflow and may cause changes to one’s iris color and longer eyelashes. Because the drug may cause inflammation, Dr. Campbell will avoid prescribing drugs in this class for those with inflammatory eye diseases such as iritis, uveitis or macular edema, but it’s less known whether it affects patients prone to inflammation elsewhere in the body.
Physicians who suspect a glaucoma medication may be causing a patient’s symptoms should refer the patient back to his or her optometrist or ophthalmologist to consider alternative glaucoma treatments, Dr. Campbell says.
“It used to be hard to find alternatives, but now we can because we have so many classes and alternatives,” Dr. Campbell says.
She also advises that if allowed, hospitalized patients should use their outpatient prescribed glaucoma medications because hospital formularies are limited. This will help avoid glaucoma progression during inpatient stays.
Dr. Campbell is available for consultations on glaucoma medication interactions by contacting Grene Vision Group at 316-684-5158.